Batman didn't trick him, he improvised his situation. The thug pushed Batman down the shaft, he grabbed onto the ledge, and as the thug looked down, he grabbed his head with his legs.

You know, I actually forgot about that. So I guess it wasn't a trick, though I have never been a fan of Batman killing to vicariously. But to that end, that scene is acceptable compared to some of the other things he does in the film.